Characterization and use of new monoclonal antibodies to CD11c, CD14, and CD163 to analyze the phenotypic complexity of ruminant monocyte subsets

• New monoclonal antibodies developed against bovine CD11c, CD14 and CD163 were used to characterize monocyte subsets in cattle, sheep, and goats.
• Bovine monocytes are comprised of multiple phenotypically distinct subsets distinguished by differential expression of CD14, CD16, CD163, CD172a and CD209.
• CD163 is a better marker than CD14 for distinguishing monocytes in sheep and goat.

The sequencing of the bovine genome and development of mass spectrometry, in conjunction with flow cytometry (FC), have afforded an opportunity to complete the characterization of the specificity of monoclonal antibodies (mAbs), only partially characterized during previous international workshops focused on antibody development for livestock (1991, Leukocyte Antigens in Cattle, Sheep, and Goats; 1993, Leukocyte Antigens of Cattle and Sheep; 1996, Third Workshop on Ruminant Leukocyte Antigens). The objective of this study was to complete the characterization of twelve mAbs incompletely characterized during the workshops that reacted with molecules predominantly expressed on bovine monocytes and use them to provide further information on the phenotypic complexity of monocyte subsets in ruminants. Analysis revealed that the mAbs could be grouped into three clusters that recognize three different molecules: CD11c, CD14, and CD163. Following characterization, comparison of the patterns of expression of CD14 and CD163 with expression of CD16, CD172a, and CD209 revealed the mononuclear cell population is comprised of multiple subsets with differential expression of these molecules. Further analysis revealed the epitopes recognized by mAbs to CD14 and CD163 are conserved on orthologues in sheep and goats. In contrast to CD14 that is also expressed on sheep and goat granulocytes, CD163 is a definitive marker for their monocytes.